Variable condenser



July. 13 1926.

W. J. THOMPSON VARIABLE CONDENSER Filed July, 13. 1923 INVENTOR 7 ATTORNEY Patented n. 13,1926.

UNITED STATES" WILLIAMJ. 'rnomrsom'or PHILADELPHIA, rnunsrriva tra.

VARIABLE counnnsna.

Application filed m is, 1923. Serial No. 651,248.

This invention relates to variable condensers and more particularly to condensers of the so-called Vernier type. This invention is particularly directed to the provision a of means whereby it is possible to secure a very fine adjustment of the Vernier element ofthe condenser unit.

As heretofore constructed, condensers of the general type to which this invention relates, consist of a frame carrying a plurality of condenser plates fixed thereto, and a rotating member carrying a plurallty of condenser plates. Theseve'ral parts are arranged so that the condenser plates carried by the rotatable member may be rotated into juxtaposition with the plates carried by the frame. The vernier attachment generally comprises one or more plates which maybe rotated with respect to plates carried by the frame, independently of the rotatable plates included in the main part of the condenser unit. A small knob usually arranged coaxially with respect to the main condenser dial, is provided for the'purpose of actuating the vernier element. After a rough adjustment is efiected by turning the main condenser knob, or dial, a fine ad ustment is secured by turning the Vernier knob.

The common construction above described is open to the important objection that it is very diflicult, if not impossible to turn the Vernier element through a very small. angle by turning the small vernier knob or dial. it a very large dial were used in connection with the Vernier attachment, it would be comparatively easy to secure a nice adjust ment, for when the circumference of such a large dial is moved through an appreciable distance, the angular displacement effected is very small in comparison with the angular displacement of a small knob or dial, the circumference of which is turned or moved through the same distance. Accordingly one of the principal objects of the present invention is to provide a relatively large dial connected to thevernier element. The preferred embodiment of my invention cornprises a condenser unit havinga knob of ordinary dimensions fixed to the main condenser shatt, and having a dial connected to the Vernier element, the diameter of the dial being substantially larger than that of the knob or dial connected to the main condenser shaft. The two dials are preferably constructed and arranged so that the over-all dimensions are substantially the same as those of an ordinary single dial.

This invention will be betterrunderstood by referring to the tollowin detailed description which is to be consldered in conjunction with the accompanying drawings,

which illustrate one embodiment of this invention, including a number of improved t'eatures of construction. In the accompanying drawings: a

Fig. 1 is a plan view of a condenser 'con structed in accordance with the present invention. I

Fig. 2 is a plan view oi" the dials shown in Fig, 1. p Fig. 3 is a transverse section taken on line 3-3 of Fig. 4: illustrating-the various details of construction.

Fig. 4; is a longitudinal section taken on line d-4 of Fig. 3.

In the embodiment of the invention illustrated in the accompanying drawings, the condenser unit comprises a framework, a main condenser element,-a Vernier element,

vand dials connected to the main condenser element and to the Vernier element. The framework comprises three posts or rods 1, of ordinary construction, these rods being inter-connected by means of two plates, 2 and 3.. A plurality of condenser plates are fixed to the rods 1 in any suitable manner;

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for example, the plates 4 may have'holes provided therein, so that the plates may he slipped onto the rods 1, suitable spacers being placed between adjacent plates, or the plates may be notched andthen slipped into grooves formed in the rods. A plurality of condenser plates 5 are fined to the shaft 6, the plates 5 together with the plates tor-in ing the main condenser element of the unit. The plates 5 may be fixed to the shaft 6 in any suitable manner, such as that described in connection with the condenser plates 4-, which are fined to the rods 1 of the frame.

A suitable bearing '3' is provided for the shaft 6. As is shown in the drawings, the bearin 7 consists of insulating material,

and it is secured to the plate 2 or the tramework by means of screws 8. A dial 3*, pro.- vided with a knob 10 of ordinary construction is fixed to theshatt 6 by means of a set screw 11.

The Vernier element illustrated in the drawings comprises two stationary lates l2 and 3 and a rotatable plate 13 which is Mitzi carried by a sleeve i l encircling the shaft 6.

The sleeve 14 is supported in a suitable bearto the plate 3 and are adapted to receive screws 21 which serve to fix the unit in po sition on a panel 22. In the embodiment illustrated in the drawing, a bushing or collar 23 is provided on the shaft 6, between the sleeve 14 and the shaft bearing 7, this bushing being held in position by means of a set screw 24:.

In assembling the several parts of my improved condenser unit, the parts comprising the framework, are first secured together in the well known manner. The rods 1 are secured to the plates 2 and 3 and the condenser plates 4 are fixed to the rods 1, as above described. If it is so desired, suitable stops 25 of insulating material may be provided on one of the rods with a view to preventing the condenser plates from coming in direct contact with each other, when the rotating member is turned to an extreme position. After the condenser plates 5 are fixed to the shaft 6 this shaft may be in sorted through the bearings 7 and 15, the bushin 23 and the sleeve 14: being slipped 'onto tie shaft 6, as it is being passed through the bearings 7 and 15. The dial 16 is slipped onto the sleeve 14 and fixed in this position by tightening the set screw- 18. The dial 9 is then slipped-onto the'end of the shaft 6 and fixed to the shaft by tightening the set screw 11.

I prefer to make the edge 25 of dial 16 quite wide and to provide this edge with a knurled surface, so that the dial may be readily turned by placin the fingers on the edge thereof. The friction of the sleeve 1% on the shaft 6 should be considerably less than that of the bearing 7 so that when the dial 16 is turned, the shaft 6 will remain stationary. Also the friction of the bearing 15 should be great enough so that when the knob 10 is turned, the dial 16 will remain stationary.

My improved condenser unit may be readilymanufactured in large quantities at assessor very low cost, for the main condenser element is composed of substantially standard parts, the shaft 6, the framework and the condenser plates being of ordinary construction.- The vernier element and the dial associated therewith are merely interposed between the main' condenser dial and the main condenser element in such a mannor that the usual construction of the main condenser parts need not be altered in any way, and the arrangement is such that it is possible to secure a' much finer adjustment of the vernier element than has been heretofore considered possible. It is quite important that the diameter of the dial or its equivalent which actuates the vernier element should be as large as possible; and this invention provides a construction such that the diameter of this dial may be made as large as desired. Throughout this application it is of course to be understood that, in speaking of the relative sizes of the condenser dials, I am referring to the over-all dimensions of the portion or portions of the dials which are grasped by the hand when the dials 'are turned.

The dial 16 may be provided with an arcuor pointer 28. The index support may be mounted on the panel 22 so as to project through the slot 26 in the dial 16. The index 28 may extend radially with respect to the dials.9 and 16 so as to'form a convenient reference mark cooperating with the graduations on both of these dials.

The size, proportions and arrangement of the several parts may be varied without dcparting from the principle of the invention, which is not limited to the particular embodiment illustrated and described, but is intended to include such modifications thereof as fall within the scope of the appended claim.

I claim:

A composite condenser dial of the type described, comprising a dial adapted to be connected to a condenser element. and a second dial arranged coaxially with respect to the first dial and adapted to be connected to a second condenser element, the said second dial being provided with an arcuate slot disposed near the edge of the first dial and adapted to receive an index support.

In testimony whereof I afiix my signature.

' WILLIAM J. THOMPSON. 

